#include<stdio.h>
int main()
{
	int n ,m,i;
	scanf("%d%d",&n,&m);
	int sum=0;
	i = n;
	for(i=n;i<=m;i++)
	{
		if(i%2==1)
		{
			sum=sum+i;
			continue;
		}
		
		
	}
	printf("%d",sum);
	
	return 0;
} 
